Dual Processor
Supervisors with Watchdog
ADM13305
Rev. 0
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FEATURES
Dual supervisory circuits
Supply voltage range of 2.7 V to 5.5 V
Pretrimmed threshold options: 1.8 V, 2.5 V, 3.3 V, and 5 V
Adjustable 0.6 V voltage reference
Maximum supply current of 40 μA
140 ms (minimum) reset timeout
Watchdog timer with 1.6 sec (typical) timeout
RESET valid from V
DD
≥ 1.1 V
Push-pull RESET and
RESET
outputs
8-lead, narrow body SOIC package
Temperature range: −40°C to +85°C
APPLICATIONS
Supervising DSPs/microcontrollers
Industrial and portable equipment
Wireless systems
Notebook/desktop computers
GENERAL DESCRIPTION
The ADM13305 is a dual voltage supervisor designed to
monitor two supplies and provide a reset signal to DSP and
microprocessor-based systems.
There are five models available, all of which feature a combination
of internally pretrimmed undervoltage threshold options for
monitoring 1.8 V, 2.5 V, 3.3 V, and 5 V supplies. There is also
an adjustable input option with an undervoltage threshold voltage
of 0.6 V.
The ADM13305-18, ADM13305-25, and ADM13305-33 models
have two internally fixed thresholds. The ADM13305-4 and
ADM13305-5 offer one internally fixed threshold and one
externally programmable threshold via a resistor string. See
the Ordering Guide for a list of all available options.
During power-up,
RESET
is asserted when the supply voltage
exceeds 1.1 V. The device then monitors the SENSEv input pins
and holds the
RESET
output low as long as either of the SENSEv
inputs remains below the rising threshold voltage, V
IT+
.
FUNCTIONAL BLOCK DIAGRAMS
06922-002
V
DD
14kΩ
R1
R2
R3
R4
1.25V
RESET
LOGIC + TIMER
OSCILLATOR
TRANSITION
DETECTION
WATCHDOG
LOGIC + TIMER
RESET
ADM13305-33
ADM13305-25
ADM13305-18
SENSE1
SENSE2
GND
WDI
MR
RESET
Figure 1.
06922-001
V
DD
14kΩ
R1
R2
0.6V
RESET
LOGIC + TIMER
OSCILLATOR
TRANSITION
DETECTION
WATCHDOG
LOGIC + TIMER
RESET
ADM13305-4
ADM13305-5
SENSE1
SENSE2
WDI
MR
RESET
GND
Figure 2. .
Once the supplies monitored at the SENSEv inputs rise above
their associated thresholds, the reset signal remains low for
the reset timeout period before deasserting. Subsequently, if a
voltage monitored by the SENSEv pins falls below its associ-
ated falling threshold, V
IT−
, the
RESET
output asserts. The
ADM13305 features both an active high RESET and an active
low
RESET
output.
As well as providing power-on reset signals, an on-chip watchdog
timer can reset the microprocessor if it fails to strobe within the
preset timeout period. A reset signal can also be asserted by an
external push button through the manual reset input pin.
The ADM13305 is available in an 8-lead, narrow body SOIC
package. The device operates over the extended industrial
temperature range of −40°C to +85°C.
